Antireflective polymer films (“AR films”) are becoming increasingly important in the display industry. New applications are being developed for low reflective films applied to substrates of articles used in the computer, television, appliance, mobile phone, aerospace and automotive industries.
AR films are typically constructed by alternating high and low refractive index (“RI”) polymer layers in order to minimize the amount of light that is reflected from the optical display surface. Desirable product features in AR films for use on optical goods are a low percentage of reflected light (e.g. 1.5% or lower) and durability to scratches and abrasions. These features are obtained in AR constructions by maximizing the delta RI between the polymer layers while maintaining strong adhesion between the polymer layers.
It is known that the low refractive index polymer layers used in AR films can be derived from fluorine containing polymers (“fluoropolymers” or “fluorinated polymers”). Fluoropolymers provide advantages over conventional hydrocarbon-based materials relative to high chemical inertness (in terms of acid and base resistance), dirt and stain resistance (due to low surface energy) low moisture absorption, and resistance to weather and solar conditions.
The refractive index of fluorinated polymer coating layers can be dependent upon the volume percentage of fluorine contained within the layer. Increased fluorine content in the layers typically decreases the refractive index of the coating layer. However, organic solvent soluble fluoropolymers with low crystallinity generally have undesired mechanical properties, such as poor scratching resistance and poor the interfacial adhesion of the fluoropolymer layer to other polymer or substrate layers to which the layer is coupled.
Thus, it is highly desirable to form a low refractive index layer for an antireflection film having increased fluorine content, and hence lower refractive index, while improving mechanical properties by crosslinking and by enhancing interfacial adhesion to accompanying layers or substrates.